Oil burner spray nozzle



Jan. 9, 1968 Filed Nov. 5, 1965 sk /0x5 s ar 4 0/1455? O. A. DAVIS, SR.ETAL OIL BURNER SPRAY NOZZLE 5 Sheets-Sheet 1 g Z 6' if 5 a INVENTORS I0I] 2 3 4 a P5P cwr owaa/v wax/0! BRUCE R. WALSH 1968 o. A. DAVIS, SR.ETAL 3,362,647

01L BURNER SPRAY NOZZLE Filed Nov; 5, 1965' 5 Sheets-Sheet z Q Q I .la j.aas I 542 i &1 V M J as I 44 :2 4 44 52 44 156.54 176.55

. INVENTORS ORVIS A. DAVIS, SR. a BRUCE R WALSH 1968 o. A. DAVIS, 5ETAL. 3,362,6 7

ZZLE

Jan. 9; 1968 Filed Nov. 3, 1965 5 Sheets-Sheet L Ila /22 ll I /24INVENTORS ORVIS A. DAVIS, SR. 8. BRUCE R. WALSH I Jan. 9, 1968 o. A.DAVIS, SR. ETAL 3,36

OIL BURNER SPRAY NOZZLE Filed Nov. 5, 1965 5 SheetsSheet 5 10 we p.478

IN VENTORS ORV/5 A. DAV/5, 54. BRUCE R. W41. 5H

United States Patent 3,362,647 OIL BURNER SPRAY NOZZLE Orvis A. Davis,Sr., Gibsonia, and Bruce R. Walsh, Wilkinsburg, Pa., assignors to GulfResearch & Development Company, Pittsburgh, Pa., a corporation ofDelaware Filed Nov. 3, 1965, Ser. No. 506,197 8 Claims. (Cl. 239-404)This application is a continuation-in-part of Ser. No. 354,506, nowpatent 3,217,986, which was filed Mar. 20, 1964 as a continuationin-partof Ser. No. 298,970, filed July 31, 1963, now abandoned.

This invention relates to novel oil burner spray nozzles. Moreparticularly, this invention relates to oil burner nozzles adapted forsuperior admixing of air into an oil spray. Still more particularly,this invention relates to oil burner nozzles adapted to aspirateatmosphereic air into the nozzle and homogeneously admix the aspiratedair into the oil spray.

It is advantageous in terms of combustion performance for burner nozzleswhich spray oil under pressure to aspirate air directly into the burnernozzle. However, pressurized oil burner nozzles which aspirate airdirectly into the nozzle can advantageously aspirate only a smallproportion of the total amount of air required for combustion and insuch nozzles increasing the quantity of air aspirated beyond a specificamount does not necessarily further improve nozzle combustionperformance. For example, it is shown in this application that as thequantity of air aspirated into an oil burner nozzle increases in aspecific range, combustion performance with the nozzle declines. Thenozzles of this invention are adapted not only for aspiration of airdirectly into an oil burner nozzle but also to accomplish thisaspiration in a manner which enables the aspirated air to exert anespecially beneficial effect upon combustion performance.

The nozzles of this invention aspirate one or a plurality of streams ofair into a forward nozzle chamber surrounding a swirling conical sprayof oil droplets. The air enters the rear of the chamber outside of theperiphery of the oil spray. The nozzles of this invention possessstructure which causes the velocity of the aspirated air to increase asit approaches the conical swirling spray of fuel oil droplets so a highdegree of admixture occurs between the air and the swirling oil spray.

Generally, in order to achieve a high degree of mixing of air into anoil spray, it is necessary to force pressurized air into the oil spray.However, if a jet of pressurized air is forced into a swirling conicaloil spray, disruption of swirling and distortion of the shape of thespray is likely. Since a fundamental feature of a swirling spray processis the inducing of a high degree of oil atomization, any interferencewith the swirling process during the introduction of air to the oilspray is likely to retard oil atomization. In accordance with thepresent invention, a high degree of mixing of air into an oil spray isachieved with a spray nozzle without interfering with the oil spraypattern or hindering the atomization procedure.

In operation, the nozzle of this invention induces aspirated air toincrease in velocity as it approaches the oil spray. An increase invelocity is imparted to the aspirated air stream directly at or veryclose to the oil spray, urging the air stream into close proximity withthe oil spray. In this manner the oil spray is tightly encircled by ablanket of air and the air is facilely positioned to be caught up by theswirling droplets in the oil spray to provide a homogeneous admixture ofoil and air with minimum disturbance of the oil spray.

This invention and the advantages thereof are illustrated by thefollowing description in reference to the drawings in which:

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FIGURE 1 is a cross-sectional view of a nozzle modified to show twotangential slots 44 in full view, and taken along the line 1-1 of FIGURE2,

FIGURE 2 is a plan view of member 14 of FIGURE 1,

FIGURES 3A and 3B are cross-sectional views of fragments ofcorresponding nozzles, the view of each nozzle being modified to showtwo tangential slots 44 in full, with FIGURE 38 showing a nozzle whichis modified with respect to the nozzle of FIGURE 3A,

FIGURE 4 shows graphs illustrating the results of combustion testsobtained with the nozzles of FIGURES 3A and 3B.

FIGURES 5A and 5B are cross-sectional views of frag ments of differentnozzles, the view of each nozzle being modified to show two tangentialslots 44 in full, with FIGURE 5B showing a nozzle which is modified withrespect to the nozzle of FIGURE 5A,

FIGURE 6 is a cross-sectional view of a nozzle,

FIGURE 7 is a cross-sectional view indicated by the line 77 of thenozzle of FIGURE 6 showing the forward end of member 74 in full, and

FIGURES 8, 9, 10 and 11 are cross-sectional views of still other nozzleswith the cutaway portions of the nozzles of FIGURES 9, 10 and 11corresponding generally to corresponding parts of the nozzle of FIGURE8.

Referring to FIGURE 1, nozzle 10 is comprised in part of three coaxialconically shaped elements including an inner cone 12, an intermediatecone 14, and an outer conical housing 16. Conical surface 18 of innercone 12 and conical surface 20 of intermediate cone 14 abut firmlyagainst each other in fluid tight engagement while conical surface 22 ofintermediate cone 14 and conical surface 24 of outer conical housing 16also abut firmly against each other in fluid tight engagement. Therearward portion of inner cone 12 comprises a stud 26 having apassageway means 28 extending axially and radially to zone 34. Aconically shaped axial swirl chamber 30 is defined between inner cone 12and intermediate cone 14. One or a plurality of shallow slots 32 extendthe length of conical surface 18 connecting zone 34 and swirl chamber30. Slots 32 approach swirl chamber 30 in a direction which issubstantially tangential with respect to the swirl chamber wall surface.A central opening at the forward end of intermediate cone 14 defines anaxial discharge orifice 36 for swirl chamber 30 leading into a second orforward chamber 38.

Second chamber 38 comprises a cylindrically shaped bore extendingaxially completely through outer conical housing 16. The base portion ofsecond chamber 38 is not coincident with but rather is removed fromconical surface 24 by means of a continuous ledge 40 lying on a planesubstantially normal to the longitudinal axis of nozzle 10. The interiorsurface of ledge 40 is coincident at one end with conical surface 24 andterminates at the other end with a relatively sharp edge 42, forexample, the right angle shown. Sharp edge 42 extends along a continuouscircular path and defines the periphery of the base of forward chamber38. Slots 44 extend from zone 46 and open into the base of forwardchamber 38. The depth of slots 44 can be tapered along the length of theslots, as shown, or the depth of slots 44 can equivalently be uniformalong the length of the slots. Ledge 40 is a partial barrier andpartially obstructs the front or discharge end of slots 44 by coveringthe portion of the terminus of slots 44 which is remote from orifice 36.Ledge 40 is sufficiently wide in relation to the depth of slots 44 attheir juncture with second chamber 38 that it constitutes a significanteffect upon flow therefrom. For example, ledge 40 may obstruct about onethird, one half, or more, of the portion of the forward opening of slots44 most remote from orifice 36. This estimate is merely illustrative andthe extent of obstruction of the terminus of air slots 44 by ledge 40can vary widely depending upon the desired operating characteristics ofthe nozzle.

One or more slots 44 are provided. Slots 44 enter the bottom of forwardchamber 38 in a generally forward direction, as shown in FIGURE 1, andalso in a direction which is substantially tangential with respect tocurved wall 48, as is shown in FIGURE 2. Orifice 36 enters chamber 38axially at the base thereof. A swirling conical spray of oil droplets 50from orifice 36 traverses the length of forward chamber 38 and leavesthe nozzle through discharge opening 52 of forward chamber 38. Opening52 is larger than orifice 36. The depth and diameter of forward chamber38 are determined by the included angle of spray 50 and are such thatthe spray 5t) passes close to but does not impinge upon the periphery ofopening 52.

Nozzle includes an outer nozzle body 54 having opening means 56extending from the atmosphere to zone 46. The nozzle elements aresecured fixedly into position by means of threaded member 58 andthreaded member 60. Member 58 has an axial bore 62 in register withpassageway means 28. Member 58, member 60 and outer nozzle body 54 arein threaded engagement, as shown, when the nozzle is assembled. Member58 is threaded over its entire length to permit connection to a sourceof pressurized fuel oil and nozzle body 54 is provided with threads formounting the nozzle during operation.

In the operation of the nozzle of FIGURE 1, oil under pressure is pumpedthrough axial passageways 62 and 28 into zone 34, whence it passesthrough slots 32 which enter swirl chamber 30 in a forwardly andtangential manner with respect to the conical wall surface of swirlchamber 30. A thin film of swirling oil is discharged through orifice 36which diverges conically in transit through forward chamber 38 anddisintegrates into very small oil droplets.

Forward chamber 38 serves as both an air aspirating and air-oil mixingchamber. The relative depth and diameter dimensions of forward chamber38 are determined by the included angle of conical oil spray 50. Thesedimensions are established so that oil spray 5t) narrowly misses theforward edge of wall 48. In this manner, a suction is created withinforward chamber 38 which draws atmospheric air through openings 56, zone46 and elongated passageways 44. If oil spray 50 impinges upon wall 48,the nozzle drips liquid oil, aspiration fails, and the nozzle becomesinoperative for practical purposes. Also, if oil spray 50 clears theouter edge of wall 48 by too great a distance, the nozzle will beincapable of effective aspiration.

When the depth and diameter dimensions of chamber 38 are established inrelation to the included angle of spray 50 so that spray 5t clears wall48 by an amount resulting in substantially optimum aspiration, a streamof air flows forwardly through elongated passageways 44, past sharp edge42, and into forward chamber 38. In passing sharp edge 42, the aspiratedair is deflected so that as it enters forward chamber 38 it is urgedclose to oil spray 50, as indicated at 51. The air deflecting functionof sharp edge 42 causes aspirated air stream 51 to be deflectedlaterally so that it closely encompasses oil spray 5th withoutdisturbing the spray or hindering oil atomization. Air stream 51 travelswith the spray in close proximity thereto so that the air is facilelyavailable to be caught up by the oil spray to provide a homogeneousadmixture of oil and air with minimum disturbance of the oil spray. FIG-URE 1 shows that the diameter of forward chamber 38 is sufiicientlylarge not only for conical spray 50 to pass through without contact withthe walls of forward chamber 38 but also for the air stream venacontracta indicated at 51 to develop around conical spray 50.

The air deflecting function of sharp edge 42 provides greatly improvedcombustion performance. In a nozzle which is otherwise incapable ofinducing a high velocity in the aspirated air stream, both the numberand the size of air passageways 44 are advantageously relatively smallin order to maintain a relatively high air velocity through each ofthese passageways. A relatively high air velocity in the region of sharpedge 42 is necessary if sharp edge 42 is to function as an orifice andadequately deflected air stream 51 in the direction of oil spray 50. Ina nozzle wherein the velocity of the aspirated air is not great, it isadvantageous to minimize the number and size of air passageway slots 44even to the extent of severely restricting the total volume of airaspirated by the nozzle, since the higher air velocity which resultsthereby induces a higher degree of air deflection with ensuing improvedair-oil mixing.

The highly superior mode of mixing air and oil provided by the nozzle ofthis invention produces better combustion characteristics than ispossible by merely aspirating a greater quantity of air in the absenceof the superior mode of mixing. Data presented below show that in anozzle devoid of the air deflecting means of this invention, a mereincrease in the quantity of air aspirated does not necessarily improvecombustion performance and, in fact, can hinder combustion performance.In contrast, superior combustion performance occurs as a result of themore thorough admixing with oil of a relatively small volume ofaspirated air which is accomplished by employing, in combination, aforward chamber 38 in which the depth and diameter dimensions areconducive to optimum air aspiration for superior mixing of air and oil,together with one or a plurality of air slots 44, each of relativelysmall cross section to provide a high air velocity therein, and a sharpedge 42 at the discharge terminus of the air slots 44.

Tests were conducted to illustrate the advantage during combustion ofthe sharp edge air deflecting means 42. A first combustion test was madeemploying a nozzle generally similar to the nozzle of FIGURES 1 and 2and having the specific construction as shown in FIGURE 3A, including asharp edge 42 disposed at the discharge end of passageway means 44.Passageway means 44 approaches second chamber 38 in both a forwardly anda tangential manner. At the conclusion of the first combustion test, thenozzle of FIGURE 3A was modified for use in a second combustion test byeliminating sharp edge 42 by machining, as shown in FIGURE 3B. Exceptfor this single change, the nozzle of FIGURE 3B is identical to thenozzle of FIGURE 3A and all conditions, including oil pressure, wereotherwise held uniform in each test. The results of these tests areshown in the curves of FIG- URE 4.

The curves of FIGURE 4 show the results of the combustion testsemploying the nozzle of FIGURE 3A and the nozzle of FIGURE 3B in theform of a graph of smoke spot number versus percent carbon dioxide in asample of flue gas produce-d during combustion with each nozzle inaccordance with the method described in ASTM Standards on PetroleumProducts, 1960, page 1041. For purposes of analyzing the test results,it is noted that best combustion results are indicated by thecombination of a high carbon dioxide content, indicating a high degreeof combustion, and a low smoke content. While the percent of carbondioxide can be increased by reduction of air input, this will have theadverse eflect of increasing smoke content. On the other hand, smokecontent can be decreased by merely admitting a large excess of air butthis will have the adverse effect of greatly diminishing the relativecontent of carbon dioxide. Optimum results are achieved with thecombination of relatively high carbon dioxide content and relatively lowsmoke content.

Referring to FIGURE 4, at the steep slope of the curves, it is seen thatat any particular percentage of carbon dioxide in the flue gas thelowest smoke content is achieved with the nozzle of FIGURE 3A havingsharp edge air deflecting means 42. Therefore, the removal of sharp edgeair deflecting means 42, as shown in the nozzle of FIGURE 3B, resultedin increased smoke content at any particular percentage of carbondioxide or, conversely, a lower percentage of carbon dioxide at anyparticular smoke level.

Another series of tests was conducted to demonstrate the ability of thesharp edge air fiow deflector of the invention to induce superiorcombustion characteristics as compared to the combustion characteristicsachieved by similar nozzles which are devoid of the air flow deflector,even nozzles which actually aspirate a greater quantity of air at agiven fuel flow rate. The nozzles utilized in these tests are shown inFIGURES 5A and 513. FIGURE 5A shows a nozzle having a sharp edge 42 andhaving a forward chamber 38 whose depth, designated as L, is 0.030 inchand whose diameter, designated as D, is 0.089 inch. These dimensionsshow that the diameter of forward chamber 38 is greater than its length.The reason the diameter of forward chamber 38 is greater than its lengthis that if L were as great as D the conical oil spray would impinge uponthe walls of forward chamber 38, as is clear from observation of FIGURE5A. Air slots 44 approach second chamber 38 in a substantially forwardlyand tangential direction. As shown in FIGURE 5A, the surface ofdischarge orifice 36 is curved and tapers outwardly in the direction offorward chamber 38 and is in direct communication with forward chamber38 for discharging a distinctly conical spray from swirl chamber 30through forward chamber 38 without interference, obstruction, or contactwith any part of said nozzle. The oil spray issuing from orifice 36 ofoil swirl chamber 30 had a 70 degree included angle and was found toexert a suction upon tangential air passageways 44 equivalent to 0.6inch of Water. As shown in Table 1, the flue gas from the nozzle ofFIGURE 5A contained 12.7 percent carbon dioxide at a smoke spot numberof 1.

FIGURE 5B shows another nozzle used in the same series of tests. Thenozzle of FIGURE 53 is similar to the nozzle of FIGURE 5A except thatthe passageways 44 are each devoid of sharp edge 42 and except that itsforward chamber 38 has certain L and D dimensions which are slightlydifferent than those of the nozzle of FIGURE 5A. The oil pressure andincluded angle of the oil spray in the tests with the nozzle of FIGURE5A were the same as in the tests with the nozzle of FIGURE 5B. Thenozzle of FIGURE 53 was utilized in two tests in which the D dimensionwas 0.089 inch and 0.101 inch, respectively. The results of these testsare shown in Table 1.

It is seen from Table 1 that the aspirational suction exerted at airslots 44 of the nozzle tested of FIGURE 5B varied considerably withdimension changes in the second chamber. It is also seen from Table 1that, in the tests made, an increase in air aspiration did not produce acorresponding improvement in combustion performance. In fact, the nozzleof FIGURE 5B which exerted an aspirational effect of only 0.3 inch ofwater was superior, in terms of combustion performance, to the othernozzle of FIGURE 5B which exerted ten times its aspirational effect uponatmospheric air. Table 1 also shows that better combustion performancewas achieved with the nozzle of FIGURE 5A, equipped with sharp edge 42at the air passageways, than was achieved with either of the nozzles ofFIGURE 5B, even though one of the nozzles of FIGURE 58 exerted a muchgreater aspirational suction upon atmospheric air. Table 1 shows thatsharp edge 42 exerts an influence upon combustion performanceindependent of the amount of air aspirated.

Combustion tests were made to determine the effect of air deflector 42when air was pumped through air slots 44 under a small pressure, such as1 or 2 pounds per square inch gauge. The tests showed combustion resultsare also improved by the provision of sharp edge air deflector 42 whenair is pumped under pressure through air slots 44.

FIGURES 6 and 7 illustrate a modified nozzle 70 of this invention.FIGURE 6 shows an inner member 72, an intermediate member 74, and anouter member 76. Outer member 76 comprises the body of the nozzle. Innermember 72 and intermediate member 74 have facing conical surfaces inengagement while intermediate member 74 and outer member 76 have flatfacing surfaces in engagement. The various facing surfaces are urgedinto fiuid tight engagement with each other by means of plug 78 which isin threaded engagement with nozzle body 76. Oil enters zone 82 throughoil passages in plug 78 whence it travels through slots 84 which enterswirl chamber 86 in a forwardly and tangential direction with respecttothe conical wall surface thereof. A diverging, conical, swirling spray38 of atomized oil droplets leaves axial swirl chamber discharge orifice90.

Oil spray 88 clears wall 92 defining the forward nozzle chamber by anamount adapted to aspirate atmospheric air through a plurality ofatmospheric air openings 94 which have access to a continuous air zone96. Each air opening 94 is in general register with an arc-like groove98 cut in intermediate member 74. As shown in FIGURE 7, each groove 98extends to the forward nozzle chamber in a generally forward andnontangential direction. Althrough each groove 98 could also extend tothe second chamber in a geneally forward and tangential direction withrespect to forward chamber Wall 92, a forward but nontangentialdirection is preferred. The front of nozzle body 76 is directed inwardlyto form a continuous circular ledge 100 having a sharp right angle edge102 at its interior face which partially obstructs the portion of eachgroove 98 remote from orifice 90 in the region of the juncture of eachgroove 98 with the forward nozzle chamber. Sharp edge 102 causesaspirated air to be de flected, as indicated at 104, so that each airstream is urged laterally against oil spray 88. The air flow deflectioncaused by sharp edge 102 causes the air streams to encompass oil spray88 so that the swirling spray of oil droplets can accept theconcurrently flowing air and become homogeneously admixed therewithwithout disruption of the oil spray.

FIGURE 8 shows a cross-sectional view of nozzle In nozzle 110, a hollow,swirling, diverging oil spray 112 issuing from first orifice 114narrowly clears the downstream end of second chamber 116 and therebyaspirates atmospheric air inwardly through a plurality of radialpassageways 118. Air passageways 118 lead into a continuous annulus 120which completely surrounds conical member 122. Air drawn inwardlythrough passageways 118 flows into annulus 120, and thence flows pastsharp right angle edge 124 which causes it to be deflected toward theoil spray 112, as is shown in FIGURE 8. FIGURE 8 shows that the outerconical surface of member 122 is continuous with and tapers rearwardlyand outwardly substantially conically from the curved and taperedsurface of discharge orifice 114 toward the rearward end of annulus 120with the forwardmost projection of the outer conical surface of member122 being substantially at the curved and tapered surface of thedischarge orifice so that an aspirated air stream drawn inwardly throughpassageways 118 and annulus 120 can approach discharge orifice 114 fromthe rear along the outer conical surface of member 122 and can closelyencompass oil spray 112 directly upon discharge of said oil spray fromdischarge orifice 114.

It is noted in regard to nozzle 110 of FIGURE 8 that oil dischargeorifice 114 is disposed rearwardly with respect to the rearward end ofsecond chamber 116. This structure provides an important functionaladvantage because the portion of oil spray 112 closest to orifice 114comprises a substantially continuous swirling film of oil. However, thisfilm tends to quickly disintegrate, resulting in atomization into agreat plurality of very small oil droplets. By virtue of the fact thatoil discharge orifice 114 is disposed to the rear of sharp edged corner124, oil spray 112 has a chance to become atomized before reaching thevicinity of sharp edge 124 and therefore before reaching the zonewherein it becomes admixed with the air stream deflected toward it bysharp edged corner 124. Since the oil is accorded an opportunity tobecome atomized before the aspirated air is deflected toward it, a highdegree of admixture of air and oil is achieved. On the other hand, ifoil discharge orifice 114 were disposed on the same plane with orforwardly with respect to air deflecting edge 124, the air passing edge124 would be deflected into an incompletely atomized film of oil andtherefore could not admix as intimately and thoroughly with the oilspray, in which case the effectiveness of sharp edge 124 would besharply diminished. In an actual test a marked improvement in combustionperformance was achieved by disposing oil discharge orifice 114 about.015 inch to the rear of the plane of sharp edge 124, as compared to theobserved combustion performance when the oil discharge orifice wasdisposed on the same plane as the sharp edge.

It is important that air passageways 118 enter continuous annulus 120 ata position therein which is decidedly to the rear of the plane on whichsharp edged corner 124 lies. Air passageways 118 should preferably enterannulus 120 at a position as close as possible to the rear of annulus120 and should have a relatively small width so that air only entersannulus 128 near the rearward end of said annulus. This permits theaspirated air to travel in a forwardly direction past sharp edge 124permitting sharp edged corner 124 to function as a sharp edged orificeplate. The forward or axial component of movement of air past sharp edge124 permits sharp edge 124 to function as an orifice plate, deflectingthe air stream and forming the vena contracta 126. On the other hand, ifair passageway 118 were disposed on about the same plane as sharp edge124, the aspirated air would approach sharp edge 124 from a directionwhich is substantially completely lateral with little or no forward oraxial component of movement, thereby preventing formation of a venacontracta.

An advantageous feature of nozzle 110 is that air passageways 118approach annulus 120 in a radial rather than a tangential direction. Atangential approach would impart swirling to the aspirated air and thecentrifugal force of a swirling air stream passing through secondchamber 116 would tend to fling the air away from the oil spray, therebycounteracting the effect of sharp edge 124 which is to deflect theaspirated air toward the oil spray.

Another advantageous structural feature of nozzle 111) is that theindividual air passageways 118 each lead into a common annulus 120,which annulus 120 is bounded by sharp edged corner 124. In this manner acircumferentially uninterrupted stream of air is deflected toward andencompasses the oil spray providing a uniform admixture of air and oil,thereby insuring a uniform flame. In contrast, if continuous annulus1211 were absent and each air passageway 118 individually approachedsharp edged corner 124, a plurality of streams of air would be deflectedtoward the oil spray rather than a circumferentially continuous blanketof air. A plurality of individual jets of air would produce alternateair-rich and air-lean streaks in the oil spray and consequently couldproduce a non-uniform flame. Continuous annulus 120 is advantageouslyutilized in a nozzle in which the velocity of aspirated air through evenan enlarged annulus is sufficiently high that sharp edge 124 can inducea vena contracta, while a plurality of individual air passages, as isshown in FIGURES 1 and 6, are required to produce individual highvelocity air jets where the velocity of the total stream of aspiratedair flowing in an enlarged annulus would not be sufficiently high for asharp edge to induce a pronounced vena contracta.

The structures shown in nozzle 130 of FIGURE 9 and nozzle 160 of FIGURE10 each produces superior results during combustion as compared tonozzle of FIGURE 8. Nozzle and nozzle 160 each possesses two opposingsharp edges facing each other across an air passageway, as contrasted tothe single sharp edge in nozzle 110 of FIGURE 8. The double sharp edgesare disposed near the juncture of a continuous air annulus and theforward chamber. The functional advantage of the two facing sharp edgesin nozzle 130 and nozzle 160 is that a double surfaced air stream venacontracta is defined at a position downstream from the sharp edgesthemselves substantially at or in very close proximity to the surface ofthe oil spray. Since the highest velocity in the air stream is at thevena contracta, the facing sharp edge structure projects the zone ofhighest air velocity downstream from itself to the region of the surfaceof the swirling oil spray, thereby inducing an unusually high degree ofadmixing of air and oil.

In nozzle 130 of FIGURE 9, curved and outwardly tapered surface 132defining the oil discharge orifice extends to a contiguous flat surface134 which extends laterally from the discharge orifice and lies on aplane normal to the axis of the oil discharge orifice. The outerperiphery of flat surface 134 defines a continuous circular sharp edge136 facing annulus 138 in the region thereof near forward chamber 140.Flat surface 134 and the oil discharge orifice are disposed rearwardlywith respect to the rearward end of forward chamber 140.

Oil spray 142 aspirates atmospheric air into the nozzle through aplurality of radial slots 144 and continuous annulus 138. Continuouscircular sharp edge 146 which is opposite from the oil discharge orificedefines the juncture between annulus 138 and forward chamber 140. Thediameter of forward chamber is substantiallly greater than the lengththereof. Continuous, circular sharp edges 136 and 146 face each otheracross the region of annulus 138 near forward chamber 140 and lie on aplane which is at an acute angle of about 45 degrees with respect to theaxis of oil spray 142. Sharp edges 136 and 146 deflect the flow ofaspirated air stream 148 to induce a circular vena contracta 150 atwhich the velocity of air stream 148 is a maximum. Vena contracta 150 isformed downstream from the sharp edges themselves and substantially ator in very close proximity to the surface of oil spray 142. In thismanner, the air stream is directed toward the surface of the oil sprayin a direction substantially normal to said surface and is at itsmaximum velocity substantially simultaneously with its impingement uponthe outer periphery of the oil spray whereby a high degree ofintermixture between the air stream and the oil spray is accomplished.Although a continuous annular aperture is defined between sharp edges136 and 146 in the most preferred embodiment of nozzle 130, thecontinuous aperture could be replaced by a plurality of smallerapertures each provided with separate facing sharp edge surfaces. If aplurality of smaller apertures are utilized, the separate facing sharpedges in each aperture could be joined to form a continuous sharp edgedorifice plate or replaced by a circular sharp edged orifice plate.

Nozzle of FIGURE 10 shows another embodiment of a double sharp edgestructure for inducing a vena contracta in an air stream substantiallysimultaneously with impingement of the air stream upon an oil spray.Referring to FIGURE 10, the curved and outwardly tapered surface 162defining the oil discharge orifice extends to fiat surface 164 whichlies on a plane normal to the axis of the oil discharge orifice. At theouter periphery of flat surface 164 a right angle sharp edge 166 isdefined. Sharp edge 166 extends as a complete circle and defines oneextremity of continuous annulus 168. Another ex- 9 tremity of annulus168 is defined by axially inturned lip 170 at the forward end 172 of thenozzle body which possesses a right angle sharp edge 174 facingcontinuous annulus 168. Sharp edges 166 and 174 lie on a plane which isparallel to the longitudinal axis of nozzle 160 and recessed laterallyfrom forward chamber 180.

Oil spray 176 aspirates atmospheric air through a plurality of radialslots 178 and annulus 168. The air enters forward chamber 180 bytraversing the aperture between facing sharp edges 166 and 174. A doublesurfaced annular vena contracta 182 is induced downstream from the sharpedges 166 and 174 substantially at or in close proximity to theperiphery of oil spray 176. Since the downstream distance from sharpedges 166 and 174 at which vena contracta 182 is formed is proportionalto the size of the aperture between the sharp edges, the maximumpermissible thickness 171 of lip 170 is limited by the size of saidaperture. By making the thickness 171 of lip 170 less than the size ofsaid aperture, and preferably less than half the size of said aperture,the vena contracta will form downstream from lip 170 and close to oilspray 176. Sharp edges 166 and 174 direct the air stream into the oilspray along a path close to flat surface 164 and in a direction which issubstantially normal to the axis of the oil spray. Since lip 170 isrelatively thin, the locale of vena contracta 182 is significantlydownstream from lip 176 and in close proximity to the oil spray so thatthe air stream impinges upon the oil spray while it is substantially atits maximum velocity, whereby intimate admixture occurs between the airstream and the oil spray.

Nozzle 190 of FIGURE 11 utilizes means other than sharp edges forimpinging an aspirated air stream upon an oil spray while the air streamis flowing substantially at its maximum velocity. In nozzle 190, thesurfaces of intermediate member 192 and outer member 194 are contouredto define a continuous circular venturi tube 196 whose axis is normal tothe axis of oil discharge orifice 198. Less advantageously, the axis ofventuri tube 196 can be inclined with respect to the axis of dischargeorifice 198 so that the venturi tube is directed toward the nozzle axisand forward chamber 202 in a forwardly as well as a lateral direction,rather than in a purely lateral or radial direction as shown. Venturitube 196 has an annular throat 200 directly at the terminal passagewayopening of venturi tube 196 in the direction of the nozzle axis andforward chamber 202. Although venturi tube 196 is preferably acontinuous annulus extending around a 360 degree are, it can be dividedinto a plurality of individual, relatively elongated venturi tubes eachhaving its throat coinciding with the terminal opening of the venturi inthe direction of forward chamber 202. Although each individual venturican approach the forward chamber in a tangential direction, it ispreferred that the approach to the forward chamber be purely radial, orforwardly and radial, rather than tangential. As is shown in FIGURE 11,the rearward wall defining venturi throat 200 and the forwardmostportion of the curved and tapered surface defining oil discharge orifice198 are connected by a substantially flat Wall surface extendingtransversely to the nozzle axis so that the rearward wall definingventuri throat 200 and the forwardmost portion of the curved and taperedsurface defining oil discharge orifice 198 lie on substantially a commonplane which is transverse with respect to the nozzle axis.

Oil spray 204 aspirates a stream of atmospheric air through radial slots206, venturi tube 196 and venturi throat 200. The aspirated air is atits highest velocity at venturi throat 200 and, since venturi throat 200is in the region of the venturi tube which is closest to the forwardchamber, the air stream enters the forward chamber while flowing at itsmaximum velocity. The air approaches oil spray 204 in a direction whichis substantially normal to the axis of the oil spray and this coupledwith the fact that it approaches the oil spray while flowing atsubstantially its highest velocity results in a high degree ofintermixture between the aspirated air stream and the oil spray.

Comparative tests were conducted using a standard commercial air bloweroil burner apparatus to compare the combustion performance of nozzles asshown in FIG- URES 9 and 10 with the combustion performance of a nozzleas shown in FIGURE 8. The nozzle as shown in FIGURE 8 which was testedwas rated at 1.0 gallon per hour of oil and an included oil spray angleof 60 degrees, and had dimensions adapted for substantially optimumcombustion performance at this rating. The noz zle as shown in FIGURE 9and the nozzle as shown in FIGURE 10 were each also rated at 1.0 gallonper hour of oil and an included oil pray angle of 60 degrees. Testsperformed under the nozzle ratings showed that under substantiallyidentical test conditions, except for the pan ticular nozzle utilized,at identical smoke spot numbers of 1.0 the nozzle as shown in FIGURE 8produced a flue gas having a carbon dioxide content of 13.1 percent; thenozzle as shown in FIGURE 9 produced a flue gas having a carbon dioxidecontent of 13.6 percent; and the nozzle as shown in FIGURE 10 produced aflue gas having a carbon dioxide content of 13.5 percent. Therefore,under the substantially identical conditions of the tests, the nozzlesof FIGURES 9 and 10 produced improved combustion results as compared tothe nozzle of FIGURE 8.

Tests were also conducted using a standard commercial air blower oilburner apparatus to compare the combustion performance of a nozzle asshown in FIGURE 11 with the combustion performance of a nozzle as shownin FIGURE 8. The nozzle of FIGURE 8 which was tested was rated at 1.10gallons per hour of oil and an included oil spray angle of 60 degrees,and had dimensions adapted for substantially optimum combustionperformance at this rating. The nozzle as shown in FIG- URE 11 was alsorated at 1.10 gallons per hour of oil and an included oil spray angle of60 degrees. Tests performed under the nozzle ratings showed that undersubstantially identical test conditions, except for the particularnozzle utilized, at identical smoke spot numbers of 1.0 the nozzle asshown in FIGURE 8 produced a flue gas having a carbon dioxide content of12.8 percent while the nozzle as shown in FIGURE 11 produced a flue gashaving a carbon dioxide content of 13.2 percent. Therefore, under thesubstantially identical conditions of the tests, the nozzle of FIGURE 11produced improved combustion results as compared to the nozzle of FIG-URE 8.

Various changes and modifications can be made without departing from thespirit of this invention and the scope thereof as defined in thefollowing claims.

We claim:

1. A burner nozzle comprising axial swirl chamber means, second chambermeans of substantially cylindrical configuration disposed forwardly withrespect to said swirl chamber means, said swirl chamber means having atits forward end axial discharge orifice means with the surface of saiddischarge orifice means being curved and tapered outwardly in thedirection of said second chamber means and being in unobstructedcommunication with said second chamber means for discharging a swirlingdistinctly conical oil spray from said swirl chamber means through saidsecond chamber means without interference or obstruction and withoutsubstantial contact with said nozzle so that said conical oil sprayaspirates a stream of air through said second chamber means from therearward end to the forward end thereof, air passageway means open atone end to the exterior of said nozzle and open at the other end in thedirection of said second chamber means for channeling air into saidsecond chamber means, said air passageway means having substantially theconfiguration of venturi means whose axis is substantially transverse tothe axis of said nozzle, said venturi means terminating with openingmeans at the throat thereof facing toward said nozzle axis in adirection substantially transverse to said nozzle axis, the rearwardportion of the wall defining said venturi throat and the forwardmostportion of said curved and tapered surface of said discharge orificelying on substantially a common plane which is substantially transversewith respect to said nozzle axis, said cylindrical second chamber meanshaving a diameter which is substantially greater than the length thereofand which is sufliciently large for the conical spray from the swirlchamber means to pass through without substantial contact with the wallsof said second chamber means and for the air stream flowing through saidventuri throat to admix with said oil spray.

2. The nozzle of claim 1 wherein said venturi means extends toward saidnozzle axis in substantially a radial direction.

3. The nozzle of claim 1 wherein said venturi means is a continuousannulus.

4. The nozzle of claim 1 wherein said venturi means comprises aplurality of individual venturi means.

5. A burner nozzle comprising inner, intermediate, and outer members,axial swirl chamber means defined by said inner and intermediatemembers, air passageway means defined by said intermediate and outermembers, said air passageway means extending to the exterior of saidnozzle, axial swirl chamber discharge orifice means defined at theforward end of said intermediate member, said outer member inturned atits forward end to define axial forward chamber means of substantiallycylindrical configuration open at its rear to said air passageway means,said swirl chamber discharge orifice means disposed in the region of therear of said forward chamber means, the surface defining said dischargeorifice means being curved and tapered outwardly in the direction ofsaid forward chamber means and being in unobstructed communication withsaid forward chamber means for discharging a swirling distinctly conicaloil spray from said swirl chamber means through said forward chambermeans without interference or obstruction and without substantialcontact with said nozzle so that said conical oil spray aspirates astream of air through said air passageway means and said forward chambermeans, said air passageway means define-d by said intermediate and outermembers having substantially the configuration of venturi means whoseaxis is substantially transverse to the axis of said nozzle, saidventuri means terminating with opening means at the throat thereoffacing toward said nozzle axis in a direction subsatntially transverseto said nozzle axis, the rearward portion of the wall defining saidventuri throat and the forwardmost portion of said curved and taperedsurface of said discharge orifice being connected by a substantiallyflat surface of said intermediate member extending substantiallytransversely to said nozzle axis, said cylindrical forward chamber meanshaving a diameter which is substantially greater than the length thereofand which is sufficiently large for both the conical spray from theswirl chamber means to pass through without substantial contact with thewalls of said forward chamber means and for the air stream flowingthrough said venturi throat to admix with said oil spray.

6. The nozzle of claim 5 wherein said venturi means extends toward saidnozzle axis in substantially a radial direction.

7. The nozzle of claim 5 wherein said venturi means is a continuousannulus.

8. The nozzle of claim 5 wherein said venturi means comprises aplurality of individual venturi means.

References Cited UNITED STATES PATENTS 1,439,320 12/1922 Morse 239-4032,551,276 5/1951 McMahan 239403 2,719,056 9/1955 Bettison 239-4032,873,099 2/1959 Wittke 239403 3,217,986 11/1965 Davis et-al 239--403FOREIGN PATENTS 682,113 11/1952 Great Britain. 298,448 7/ 1954Switzerland.

EVERETT W. KIRBY, Primary Examiner.

1. A BURNER NOZZLE COMPRISING AXIAL AND SWIRL CHAMBER MEANS, SECOND CHAMBER MEANS OF SUBSTANTIALLY CYLINDRICAL CONFIGURATION DISPOSED FORWARDLY WITH RESPECT TO SAID SWIRL CHAMBER MEANS, SAID SWIRL CHAMBER MEANS HAVING AT ITS FORWARD END AXIAL DISCHARGE ORIFICE MEANS WITH THE SURFACE OF SAID DISCHARGE ORIFICE MEANS BEING CURVED AND TAPERED OUTWARDLY IN THE DIRECTION OF SAID SECOND CHAMBER MEANS AND BEING IN UNOBSTRUCTED COMMUNICATION WITH SAID SECOND CHAMBER MEANS FOR DISCHARGING A SWIRLING DISTINCTLY CONICAL OIL SPRAY FROM SAID SWIRL CHAMBER MEANS THROUGH SAID SECOND CHAMBER MEANS WITHOUT INTERFERENCE OR OBSTRUCTION AND WITHOUT SUBSTANTIAL CONTACT WITH SAID NOZZLE SO THAT SAID CONICAL OIL SPRAY ASPIRATES A STREAM OF AIR THROUGH SAID SECOND CHAMBER MEANS FROM THE REARWARD END TO THE FORWARD END THEREOF, AIR PASSAGEWAY MEANS OPEN AT ONE END TO THE EXTERIOR OF SAID NOZZLE AND OPEN AT THE OTHER END IN THE DIRECTION OF SAID SECOND CHAMBER MEANS FOR CHANNELING AIR INTO SAID SECOND CHAMBER MEANS, SAID AIR PASSAGEWAY MEANS HAVING SUBSTANTIALLY THE CONFIGURATION OF VENTURI MEANS WHOSE AXIS IS SUBSTANTIALLY TRANSVERSE TO THE AXIS OF SAID NOZZLE, SAID VENTURI MEANS TERMINATING WITH OPENING MEANS AT THE THROAT THEREOF FACING TOWARD SAID NOZZLE AXIS IN A DIRECTION SUBSTANTIALLY TRANSVERSE TO SAID NOZZLE AXIS, THE REARWARD PORTION OF THE WALL DEFINING SAID VENTURI THROAT AND THE FORWARDMOST PORTION OF SAID CURVED AND TAPERED SURFACES OF SAID DISCHARGE ORIFICE LYING ON SUBSTANTIALLY A COMMON PLANE WHICH IS SUBSTANTIALLY TRANSVERSE WITH RESPECT TO SAID NOZZLE AXIS, SAID CYLINDRICAL SECOND CHAMBER MEANS HAVING A DIAMETER WHICH IS SUBSTANTIALLY GREATER THAN THE LENGTH THEREOF AND WHICH IS SUFFICIENTLY LARGE FOR THE CONICAL SPRAY FROM THE SWIRL CHAMBER MEANS TO PASS THROUGH WITHOUT SUBSTANTIALLY CONTACT WITH THE WALLS OF SAID SECOND CHAMBER MEANS AND FOR THE AIR STREAM FLOWING THROUGH SAID VENTURI THROAT TO ADMIX WITH SAID OIL SPRAY. 